Catalytic decomposition of hydrocarbons



Patented May 19, 1953 CATALYTIC DECOMPQSITION OF HYDBOCAEBONS James H. Shapleigh, Wilmington, vDeL, ,assignor to Hercules ROWdCI Company, Wilmin n, Bet, a corporation of Delaware .No Drawing- ,Qriginal pp ic ion May "18, .1946,

Serial No. 6705839. Divided and this application August 4, "1951, Serial No. 240,458

Sillaims. 1

This invention relates to the catalytic decomposition of hydrocarbons and, more particularly, 'to a process for reacting hydrocarbons and water vapor in the presence of a catalyst which has a relatively high resistance to sulfur poisoning. The commercial preparation of hydrogen by the decomposition of hydrocarbons hasassumed great importance in industrial chemical operations, such as the synthesis of ammonia from nitrogen and hydrogen, the hydrogenation of vegetable oils,the hydrogenation oinaturalresins to give products with improved characteristics,

the synthesis of alcohols, and the like.

Heretofore, the decomposition of hydrocarbons for this purpose has been accomplished by contacting a gaseous mixtur of steam and hy- 'drocarbon at elevated temperatures, preferably with a nickel catalyst, either alone or combination with other materials such as magnesia, aluminum oxide, pumice, etc.,-to act as promoters and/or carriers. Temperatures lower than "700 C. have normally been sought to prevent 'deteriori-ation of the catalyst by rsintering or 7 other change :in physical form and to prevent the formation of excessive amounts of carbon monoxide. The-use of'such catalytic compounds has proven quite satisfactory in the reaction of yd ocarbons substantially free of sulfur and/or sulfur compounds. However, when sulfur is present, it is well known that these catalysts are poisoned and that considerably lower conversion yields would be obtained if the sulfur were not removed. It has, therefore, been necessary :to utilize hydrocarbons substantially free of ,sulfur :or sulfur compounds or else {to provide suitable preliminary treatments for removing the sulfur. 'filZhis :is both expensive and time consumin and has prevented the use of many hydrocarbons which were otl'ierwise suitable for the purpose. Consequently, a highly sulfur-resistant catalyst is greatly in demand to provide an economical process .for utilizing these sulfur-containing hydr'ocarbons.

It has been discovered that a process utilizing a catalyst comprising nickel, zirconium silicate and magnesia gives a substantial improvement in overcoming the aforementioned disadvantages. This process may be operated continuously so as to bring about a high percentage of conversion of the hydrocarbon constituents and with a reduced sulfur poisoning effect as compared to previous processes utilizing nickel catalysts.

In accordance with this invention, therefore, decomposition of the hydrocarbon is efiected by passing a heated mixture of gaseous hydrocarsilicate, and ma nesium xid .ed while-th m w s-rap dl ag tatedbon .and steam in contact w t a vcata s i ma s rial comprisin a mixtu e of ni el, z. mqnillm Fo reaso .fiully appr ciat d, t es ca al st have me owed r sistanc to su u o n n The n clielezirconium :sil cat wma nesi sa iyst o this invention m y be prepa d. za prd ing to one method, 'l-bymelting Kfil .ll ilifiii' fi zhexahsdrate in its .water o crysta liza on asizmi'sing therewith the ma nesi and than ps GiIuDg the resul in amassi lhe c lcine mess m edend-thenaddedztoth ime te n .6. ,hex-ahydrate. This mix ur :16 11111. 2 :DfilQlilfid, broken up, screened a d lleted lasi efore- "Ihe pelleted catalyst, which may he prepared in accordance with the above metho S minced e-in :a suitably :heated. cracking :tube throu h finish a mixture of steam and hydrocarbon ispassed according :to conventional methods.

Having described s-the invention generally, ithe -iol1owing examples are given sto illustrate .cific.embodimentsrthereof:

Examp 1 T ree hundr d p r-t by wei h 9 Ni(NO3) 2:6H2O

.wasplaced-m a mixing Homeland-heated 1 3 F. nightmare bvwgighiqfimalgnesia'msmd' bran e driven-mixer. The cream muted into dryin mans an p aced @a steam 'hgimg ,dryenfor 1st) 20.-h urs.a ate erat eQ -abou 2MP F. The dried c ke .was .broken cu and Ji l? throu h aealcine zat .59 48 0? The calcined;powde wa wmiiied'wifihrhim nillm silicate and additional magnesia in amounts ivaa final-mixture containin -25% :niokel. 25% zirconium .silicate, and 5 50% @ma nesia. .nfter mixing the dry powders, 30 pounds of water for each pounds of powder were added, the-whole- 3 the form of pellets. The finished pellets were placed in a cold calciner or a cold furnace tube and the temperature slowly brought up to a minimum of 1100 F. They were then cooled and were ready for use.

The pellets were placed in the reaction tube of a cracking furnace and a mixture of steam and propane in a volume ratio of 2:1, expressed as volume of steam to carbon in the gas, passed over the pellets at a space velocity of 500 volumes of steam-propane mixture per volume of catalyst per hour and a tube wall temperature of 800 C. (1472 F.). The unpoisoned catalyst gave 97% conversion of the carbon in the propane.

Sulfur as HzS was then added to the propane at the rate of 100 grains of sulfur per 100 cubic feet of propane feed. After 7 hours of contact with H28 the percentage conversion had leveled oil at 90%.

Under similar conditions, a nickel-magnesia catalyst containing 25% nickel and 75% magnesia dropped from an initial conversion rate of 98% to a subsequent conversion rate of 85% within 4 hours after sulfur was first introduced in the form of HzS and was still decreasing.

The preferred catalyst in accordance with this invention will comprise from about 10% to about 50% nickel, from about 20% to about 80% zirconium silicate, and from about 10% to about 30% magnesia. However, these percentages are not critical. It has been found, for example, that some improvement in sulfur resistant properties is obtained when the catalyst contains as little as about nickel.

The improved catalyst of this invention may be utilized in any of the known systems for decomposing hydrocarbons to form hydrogen and oxides of carbon. Normally this will consist of a plurality of externally heated tubes into which the catalyst is charged and through which a heated gaseous mixture of steam and hydrocarbon is passed.

The conversion of the hydrocarbons to hydrogen and oxides of carbon over the catalyst is conducted at conventional temperatures, space velocities, and steam-gas ratios, for example, temperatures from about 700 to 800 C.; space velocities in the order of 500 volumes per hour per volume of catalyst; and steam-gas ratios from 2:1 to 4:1 expressed as volume of steam to carbon in the hydrocarbon.

An important advantage of this invention resides in the fact that a catalyst comprisin nickel 'in combination with zirconium silicate and magin the fact that the catalyst has a high resistance to sintering or other physical change caused by exposure to high temperatures. Thus, the utilization of high temperatures i possible without substantially effecting the activity of the catalyst.

The word conversion as used herein is meant to designate the percentage of carbon in the hydrocarbons which is converted into oxides of carbon during the treatment.

This application is a division of copending application Serial No. 670,839, filed May 18, 1946, now U. S. Patent 2,575,324, issued November 20, 1951.

What I claim and desire to protect by letters Patent is:

1. The process of decomposing a hydrocarbon to form hydrogen which comprises passing a gaseous mixture of hydrocarbon and steam over a heated catalyst comprising zirconium silicate, magnesia and from about 5% to about 50% of nickel.

2. The process of decomposing a hydrocarbon to form hydrogen which comprises passing a gaseous mixture of steam and hydrocarbon over a heated catalyst comprising from about to about 50% nickel, from about 10% to about 3 magnesia, and from about to about 80% zirconium silicate.

3. The process of decomposing a hydrocarbon to form hydrogen which comprises passing a gaseous mixture of steam and hydrocarbon over a heated catalyst comprising about nickel, about 15% magnesia, and about 60% zirconium silicate.

4. A process for the catalytic decomposition of hydrocarbons which comprises reacting a gaseous mixture of steam and hydrocarbon at a temperature between about 700 C. and about 800 C. in the presence of a catalyst comprising from about 10% to about nickel, from about 10% to about 30% magnesia, and from about 20% to about 80% zirconium silicate.

5. A process for the catalytic decomposition of hydrocarbons which comprises reacting a gaseous mixture of steam and hydrocarbon at a temperature between about 700 C. and about 800 C. in the presence of a catalyst comprising about 25% nickel, about 15% magnesia, and about zirconium silicate.

JAMES H. SHAPLEIGH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,948,338 Davis et a1 Feb. 20, 1934 1,970,695 Freyermuth Aug. 21, 1934 2,028,326 Hanks et al Jan. 21, 1936 2,125,743 Sweeney et al Aug. 2, 1938 2,417,164 Huber Mar. 11, 1947 2,489,334 Shubaker Nov. 29, 1949 FOREIGN PATENTS Number Country Date 317,391 Great Britain June 16, 1930 

1. THE PROCESS OF DECOMPOSING A HYDROCARBON TO FORM HYDROGEN WHICH COMPRISES PASSING A GASEOUS MIXTURE OF HYDROCARBON AND STEAM OVER A HEATED CATALYST COMPRISING ZIRCONIUM SILICATE, MAGNESIA AND FROM ABOUT 5% TO ABOUT 50% OF NICKEL. 